Every battery has its own internal resistance. Think like speakers in your car radio (or other), 8 ohm speakers, 4 ohm speakers, etc and to get the most efficient system you have to match the speaker with the amp, i.e. 8 ohm speaker for an 8 ohm amp.
Same with batteries and loads. So the most efficient use of a battery will be the load that's closest to its impedance. So if different brands of batteries are constructed differently and have a different impedance than each may be different for the same device. Some batteries might work better with lights, others with remotes, etc. That's why you get such a variation. And I'm trying to over simplify so as to not write a novel

My own testing several years ago when eneloops were new, with the 2000mAh original version, ran my etrex at a bit over 23 hours and Energizer lithium around 24 hours. So close enough that there wasn't any benefit to using Lithium, and the cost benefit of using rechargeable is so much greater. However, I did only test indoor, just putting in a fresh pair of batteries, turning it on and setting a timer to check once an hour. Garmin published ~24 hour runtime so I started on a Saturday estimating about 8 hours before I'd go to bed then sleep for ~8 hours and get up Sunday morning at 16 hours in so I could check every hour until it died.
I suppose another test I could try with it in the refrigerator, though all my Eneloops are > 10 years old now so I expect they would also show reduced runtime.

So lights I may get different results due to factors like impedance matching, but at least with my GPS NiMH close enough to Lithium to just use them.